[MIPS] Lasat: Convert pvc_sem semaphore to mutex

I also changed the name to pvc_mutex, and moved the define to the file
it's used in which allows it to be static.

Signed-off-by: Daniel Walker <dwalker@mvista.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/lasat/picvue.h

@@ -4,8 +4,6 @@
  * Brian Murphy <brian.murphy@eicon.com>
  *
  */
-#include <asm/semaphore.h>
-
 struct pvc_defs {
 	volatile u32 *reg;
 	u32 data_shift;
@@ -45,4 +43,3 @@ void pvc_move(u8 cmd);
 void pvc_clear(void);
 void pvc_home(void);
 
-extern struct semaphore pvc_sem;